Machining center

ABSTRACT

A machining center includes a number N of workpiece tables. A number N of first guides extend parallel to a first direction. Along the first guides is movable respective to workpiece tables, one for each first guide. A number N-1 of second guides extend parallel to a second direction transverse to the first direction. A number N-1 of machining groups each include at least one machining head. Each machining group is movable parallel to the second direction along a respective second guide. A number N×(N-1) of machining areas is provided. The machining groups can operate on workpieces present on the tables. Along each first guide, or for a respective table, there is present N-1 machining areas, one for each machining group, so that each machining group can operate, according to a programmed work cycle, on all the N workpiece tables.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 37 CFR 1.53(b) of pending prior U.S. patent application Ser. No. 15/648,809 filed Jul. 13, 2017, which claims the priority of Italian Application 102016000074396, filed Jul. 15, 2016, the entire contents of each application are incorporated herein by reference.

TECHNICAL FIELD

This invention relates to the field of numerically controlled machining centers, particularly but not exclusively in the wood machining sector. More particularly, an object of the invention is a numerically controlled machining center, with 3 or more machining axes, and also a machining method associated with numerically controlled machining centers, particularly but not exclusively for machining wooden workpieces.

TECHNICAL BACKGROUND

As is well known, for machining wooden workpieces for many years there have been used numerically 3 or more axes control centers. Among the multitude of well-known machining center types are known for example machining centers which comprise two workpiece tables movable parallel among each other on respective guides.

Transversally to these guides there is a portal structure on both sides of which, front and rear, are arranged with respective machining heads equipped with one or more tool-holder spindles. The machining heads can move, for example, according to two axes, that is to say a vertical axis z and a horizontal axis x orthogonal to axis y of the table movement along the respective guide; therefore, by combining the table e and the head movements, machining on the workpiece on the table can be made according to three axes. Obviously, it is also possible that the machining heads are equipped with rotational movements, for example a rotation about axis z and a rotation about axis x, obtaining machining according to 5 axes

From an operational point of view, the two heads perform, for example, two different machining pieces on the two tables. For example, a piece is loaded on a table and another piece is loaded on the other table. The first table is moved under a first head for a first machining, while the second table is moved under the second head for a second machining. Therefore, each table is moved to a different position along its guide to be able to perform the machining with the other head (which therefore moves towards the new table) to perform the missing machining The tables then return to the loading/unloading position of the workpieces, where the machined workpiece is unloaded and a new piece is loaded.

The same machining center can be performed in double mode, that is to say four tables, four guides and four machining heads on a longer portal structure, with two heads per side, with the same operation described above (practically, it is as if two machining centers were placed alongside, as described above).

This type of machining center, although known and appreciated for many years, has limitations.

In fact, it is evident that during the loading/unloading step of a table, at least one machining head does not operate, missing its table with the workpiece.

In addition, this machining center, although it can be replicated on a larger scale, for example by doubling the number of tables and heads, is not particularly efficient in terms of head weight balancing, especially in the case of many tool changes.

SUMMARY

An object of this invention is to solve the problems and improve the limitations in machining centers, particularly but not exclusively for machining wooden workpieces, of the known type.

Within this object, an important purpose of this invention is to provide a machining center that allows optimizing production times by reducing downtimes as much as possible.

Another important object of this invention is to provide a machining center that allows increasing production.

Last but not least, purpose of this invention is to provide a method of making mechanical machining on numerical controlled machining centers, particularly but not exclusively, for machining wooden workpieces that allows increasing production. This object, these purposes and others, which will be clearer further down, are reached with a machining center that comprises:

a number N of workpiece tables equal to or greater than three,

a number N of first guides, which extend parallel to a first direction; each table being movable along a respective of said first guides,

a number N-1 of second guides, which extend parallel to a second direction transverse to said first direction,

a number N-1 of machining groups each comprising at least one machining head; each machining group being movable parallel to said second direction along a respective of said second guides;

a number N×(N-1) of machining areas in which the machining groups can machine the workpieces present on said tables; along each first guide, or for a respective table, there being present N-1 machining areas, one for each machining group, so that each machining group can operate, according to a programmed work cycle, on all said N workpiece tables,

a number N of workpiece loading/unloading areas, one for each workpiece table.

Practically, the machining center can be taken as a “matrix” structure in which the first guides represent the matrix columns and the second guides represent the matrix lines and in which the tables translate on the first guides and the machining groups translate on the second guides and in which each machining group does not operate on multiple tables simultaneously, but always operates on one table at a time. In doing so, being present one table more with respect to the machining groups, there is the possibility of scheduling machining center operating cycles so that a table is in the unloading and loading step of the piece(s) to be machined while on the others machining take place by machining groups. Practically, the unloading and loading of the workpieces takes place at a “masked” time while machining on the other tables takes place at full benefit of the machining center productivity and the timing of machining

In fact, suitably, the center comprises an electronic control group, on which there is preferably a cycle travel program of said tables which comprise, for each table:

a) positioning in said unloading/loading area, for each unloading/loading at least one workpiece on said table,

b) the translation from said unloading/loading area towards a said machining area along a corresponding first guide and positioning in said machining area in which programmed machining can be made from a given machining group,

c) translating towards another operations area along the corresponding first guide and positioning in said other machining area in which machining operations from another given machining group can be made,

d) if there is a further machining area distinct from the previous machining areas on which the table has already been positioned, the translation towards said further machining area and the positioning in said further machining area in which the programmed machining from a further machining group; this step d) being repeated iteratively until there are no longer any machining areas where the table was not positioned during the cycle,

e) translation towards said loading/unloading area to resume the cycle from step a).

Preferably, positioning of said tables on said machining areas being coordinated so that two tables never occupy two machining areas on which the same machining group can operate.

Preferably, workpieces from the machining center may be of the elongated type, that is to say in which a longitudinal dimension prevails over the other two, or even develop predominantly in two dimensions, such as, for example, window and door frames. It is to be understood that even other types of workpieces of the most varied shape can be loaded and machined on the machining center tables according to the invention.

According to preferred embodiments, the machining center comprises at least a portal structure arranged transversely with respect to the first guides; on at least one side of the portal structure is movable in parallel to said second direction, on a respective second guide, a said machining group. Preferably, the portal structure is superimposed on an intermediate position of the first guides, so that the tables are movable on the first guides under the portal structure, by passing from one side to the other of said portal structure; possibly said tables being able to position themselves at least partially under said portal structure.

Preferably, on each side of the portal structure is movable in parallel to the second direction, a respective machining group; on each side is arranged a respective of said second guides. Alternatively, to such portal structure is associated a single machining group arranged on said second guide and provided on a single side of said structure.

The machining heads have numerically controlled machining axes. The movement of the tables is numerically controlled.

According to preferred embodiments, at least one machining head of at least one of said machining groups of the portal structure is of the type:

with two machining axes, with a first vertical translation axis and a second horizontal translation axis corresponding to the axis of the second guide on which it is movable, so that, in combination with the axes corresponding to the movement of the tables along the respective first guides, said machining center is at least at 3 machining axes; or

with four machining axes, with a first vertical translation axis and a second horizontal translation axis corresponding to the axis of the second guide on which it is movable, a third rotation axis (preferably horizontal parallel to said first direction) and a fourth rotation axis, (preferably in rotation on a vertical plane about said second axis) so that, in combination with the axes corresponding to the movement of the tables along the respective first guides, said machining center is at least at 5 machining axes.

According to preferred embodiments, at least one of said machining groups comprises a single machining head.

According to preferred embodiments, at least one of said machining groups comprises two machining heads, movable independently of one another in parallel to said second direction.

According to preferred embodiments, the N loading/unloading areas of the workpieces are provided in the first end areas of said first guides. Preferably, the center comprises also a bearing structure provided in the second end areas of said first guides, on the opposite side with respect to said first end areas; on said bearing structure is provided at least one said second guide for a respective machining group; preferably this bearing structure is:

a) a portal structure that is positioned over the second end areas of said first guides, or

b) said load bearing structure facing said second ends of said first guides, without being positioned over them; preferably the machining group movable on said load bearing structure comprising at least one machining head with at least three axes, a first vertical translation axis and a second horizontal translation axis corresponding to the axis of the second guide on which it is movable, and a third translation axis parallel to said first direction, another two rotation axes being optionally possible.

According to another aspect, the invention relates also to a method for making mechanical machining by means of a machining center according to one or more of the above-mentioned embodiments or configurations, or combinations thereof.

According to this aspect, the invention relates also to a method for making mechanical machining by means of a machining center comprising:

a number N of workpiece tables equal to or greater than 3, each translatable parallel to a first direction,

a number N-1 of machining groups each comprising at least one machining head; each machining group being translatable parallel to a second direction;

a number N×(N-1) of machining areas in which the machining groups can machine workpieces present on said tables;

a number N of loading/unloading areas of the workpieces, one for each workpiece table, said method providing, for each table, the following steps:

a) positioning in said unloading/loading area, to load at least one workpiece onto said table,

b) translation from said unloading/loading area towards a said machining area and positioning in said machining area in which programmed machining operations can be carried out by a given machining group,

c) translation towards another machining area along the corresponding first guide and positioning in said other machining area in which programmed machining operations can be carried out by another given machining group,

d) if a further machining area is present, distinct from the preceding machining areas on which the table has already been positioned, translation towards said further machining area and positioning in said further machining area in which programmed machining operations can be carried out by a further given machining group; this step d) being repeated iteratively until there are no more machining areas in which the table has not been positioned during the cycle,

e) translation towards said loading/unloading area to unload the at least one machined workpiece and restart the cycle from step a).

Preferably, positioning of said tables on said machining areas being coordinated so that two tables never occupy two machining areas on which the same machining group can operate.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic side view of a first embodiment of a machining center according to the invention, with the workpiece tables in a first configuration corresponding to step 1 of the machining cycle;

FIG. 2 is a schematic rear view of the machining center of FIG. 1, in the same configuration;

FIG. 3 is a schematic top view of the machining center of FIG. 1, in the same configuration;

FIG. 4 is an arrangement diagram of the workpiece tables in a first step of a complete machining cycle, relative to a machining center as in the previous Figures;

FIG. 5 is an arrangement diagram of the workpiece tables in a second step of a complete machining cycle, relative to a machining center as in the previous Figures;

FIG. 6 is an arrangement diagram of the workpiece tables in a third step of a complete machining cycle, relative to a machining center as in the previous Figures;

FIG. 7 is an arrangement diagram of the workpiece tables in a fourth step of a complete machining cycle, relative to a machining center as in the previous Figures;

FIG. 8 is a schematic top view of a second embodiment of a machining center according to the invention, with the workpiece tables in a first configuration;

FIG. 9 is a schematic side view of a third embodiment of a machining center according to the invention, with the workpiece tables in a first configuration corresponding to step 1 of the machining cycle;

FIG. 10 is a schematic top view of the machining center of FIG. 9, in the same configuration;

FIG. 11 is a schematic side view of a fourth embodiment of a machining center according to the invention, with the workpiece tables in a first configuration corresponding to step 1 of the machining cycle;

FIG. 12 is a schematic top view of the machining center of FIG. 11 in the same configuration;

FIG. 13 is an arrangement diagram of workpiece tables in a first step relating to a complete machining cycle relating to a machining center as in FIGS. 11 and 12;

FIG. 14 is an arrangement diagram of workpiece tables in a second step relating to a complete machining cycle relating to a machining center as in FIGS. 11 and 12;

FIG. 15 is an arrangement diagram of workpiece tables in a third step relating to a complete machining cycle relating to a machining center as in FIGS. 11 and 12;

FIG. 16 is an arrangement diagram of workpiece tables in a fourth step relating to a complete machining cycle relating to a machining center as in FIGS. 11 and 12;

FIG. 17 is an arrangement diagram of workpiece tables in a fifth step relating to a complete machining cycle relating to a machining center as in FIGS. 11 and 12;

FIG. 18 is a schematic side view of a fifth embodiment of a machining center according to the invention, with the workpiece tables in a first configuration corresponding to step 1 of the machining cycle, and the machining steps thereof are similar to those shown in FIGS. 13 to 17; and

FIG. 19 is a schematic top view of the machining center of FIG. 18, in the same configuration.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the above cited Figures, a workpiece center for machining wooden workpieces is generally indicated by number 10.

EXAMPLE 1

Machining center 10 comprises a number N equal to three, of first rectilinear G1, G2 and G3 guides, which extend parallel to a Y horizontal direction. The development directions of each first guide, that is to say the handling directions of the T tables, are indicated respectively by y1, y2 and y3.

On these first G1, G2 and G3 guides (hereinafter, when referring to all three, or indifferently to one or the other, they will also be indicated simply with G), are assembled respective T1, T2 and T3 workpiece tables, one for each guide (hereinafter, when referring to all three, or indifferently to one or the other, they will also be indicated simply with T). Each table can carry one or more P pieces (only shown in the top views, that is to say, in Figures from 3 to 7).

Preferably, such P pieces can be of the elongated type, that is to say, in which a longitudinal dimension prevails over the other two, or even develop predominantly in two dimensions, such as for example in window and door frames. It must be understood that even other types of pieces of the most varied shape can be loaded and machined on the machining center tables according to the invention.

The T tables can be translated on the numerically controlled G guides.

A portal type bearing structure is generally indicated by numeral 11. This portal structure 11 is arranged transversally, in an orthogonal mode, to the first G guides. More particularly, this portal structure 11 is arranged in an intermediate position to the G guides so that the T tables are movable on the first G guides under the portal structure, being able to pass from the front side 12 to the latter's rear side 13, and vice versa, or positioning itself partially under that portal structure, if necessary.

On two front and rear sides 12 and 13 of the portal structure 11, there are two second guides W1 and W2 (hereinafter, when referring to both, or indifferently to one or the other, they will also be indicated simply with W), one for each side, which develop parallel to a second X direction, horizontal and orthogonal to the first Y direction.

On these second W guides, are arranged two movable machining groups, one for each side, respectively indicated with K1 and K2 (hereinafter, when referring to both, or indifferently to one or the other, they will also be indicated simply with K). Each K machining group can move independently of each other and can move indifferently over either of the first G guides so that they can operate on both T tables. Each K machining group operates only on one table at a time, as it will be clearer further down.

In this example, the K1 and K2 machining groups each include a machining head, respectively indicated by H1 and H2 (hereinafter, when referring to both, or indifferently to one or the other, they will also be indicated simply with H). The development directions of the second W1 and W2 guides, that is to say the translation directions of the K groups or H heads, are indicated with x1 and x2 and are marked, for simplicity's sake, on the H heads. These machining heads can be of one spindle 15 type or more than one spindle, according to known types. Tool holder storages 18 can be present, for example arranged along the portal structure.

The H machining heads can be two or more machining axes. For example, H1 head has a first vertical translational axis z1 and a second axis of horizontal translational corresponding to axis x1 of the second guide W1 on which it moves, so that in combination with the axes y1, y2, y3 corresponding to the movement of T1, T2 and T3 tables along their respective first G1, G2 and G3 guides, the machining center is of the type of at least 3 machining axes. It is also possible to add to H head the other machining axes. For example, the H1 head can have a third rotational axis g1 parallel to the first Y direction and a fourth rotation axis r1 parallel (or coincident) to the vertical translation axis z1, so that, in combination with rotation axis y1 corresponding to the movement of T1 table the machining center 10 is at least at 5 machining axes.

Each H head is movable, independently of the other, on the respective second W guide according to its direction x1 or x2, so that it can operate on both T tables.

By combining the movement of tables T and of the K (or H heads) machining groups, in the machining center 10, 3×2=6 machining areas are defined, in which the K machining groups can operate on the P pieces on T tables; these machining areas are shown from the top in a “matrix” diagram in Figures from 4 to 7 and indicated by letter J and a pair of subsequent numbers where in the first number corresponds to the number relative to the first guide along which moves a table, while the second number corresponds to the number related to the second guide along which a machining group moves (for example, T1 table moves on the first G1 guide and the K2 machining group moves on the second W2 guide, so that the machining area defined by the movement of the K2 machining group and the movement of T1 table is designated J12). These machining areas are practically the spaces occupied by the tables during machining with the groups and do not correspond only to a fixed position of the tables.

More in detail, in this example, along each first guide G, that is, for a respective T table, there are two machining areas, one for each machining group, so that each K machining group (that is, the respective machining H heads) can operate, according to a programmed machining cycle, on both workpiece T tables, preferably in a non-contemporary manner.

In the first end areas of the first G1, G2 and G3 guides, the F10, F20 and F30 loading/unloading areas of the respective T tables are defined (hereinafter, when referring to both, or indifferently to one or the other, they will also be indicated simply with F). The Figures show an operator handling unloading and loading operations, but it is evident that such operations can also be performed by automatic loading/unloading systems, for example of the known type.

Suitably, there is a protection guard 16 surrounding the machining center. The F loading/unloading areas are outside the protection guard 16, in order to allow an operator to handle the loading and unloading operations.

Machining center 10, comprises, as it is obvious, an electronic control unit, not shown in the Figures, suitable for the management of the center thereof. An advantageous program is provided on this center, which manages the T table coordinated movement cycles to make the machining through the K machining groups, which allows optimizing the machining times by reducing downtimes.

From a practical point of view, according to the invention, there is a K machining group number lower by one unit with respect to the number of tables (and corresponding loading/unloading areas), with the same groups that can anyway operate on all tables (a machining group cannot operate simultaneously on multiple tables).Therefore, it is possible to program the machining center so that when a table is at the unloading step, the other two are engaged in operating with distinct machining groups, so that each table is engaged, after the loading of the workpiece, first with one machining group and then with the other machining group, before returning to the unloading position of the just finished machining workpiece.

See the concrete example described below. As previously mentioned, Figures, from 4 to 7, show a “matrix” diagram of the machining center, in which the columns represent practically the first G guides, while two lines represent the W guides on which run the K groups or the machining H heads. The crossings of such lines with the columns represent in practice the J machining areas.

For example, with reference to FIG. 4 (step 1), and referring to a cycle time not corresponding to the machine startup, T1 table is in machining area J11, or it is interacting with K1 group, or with H1 head to allow P workpiece, loaded thereon, to undergo a first machining; T2 table is in J22 area where it is interacting with K2 group, that is, H2 head, to operate on the respective workpiece a second machining, while T3 table is in the F30 loading/unloading area to unload a just finished machining workpiece and load a P workpiece to be machined.

Subsequently (FIG. 5, step 2), table 1 is moved to J12 machining position to interact with machining H2 head (moved to this position from the previous J22 position) and perform the second machining on the workpiece, while T3 table is moved to J31 position to interact with H1 head and perform the first workpiece machining. Instead, T2 table is moved to F20 loading/unloading position to unload the workpiece that has undergone both machining operations from H1 and H2 heads.

Subsequently (FIG. 6, step 3), T1 table, wherein the machining workpiece has finished being machined, is moved to the F10 loading/unloading position to unload the workpiece and load the new workpiece. T2 table is moved from F20 loading/unloading position to machining J21 position to interact with H1 head and perform the first machining on the respective workpiece. T3 table is moved to J32 machining position to perform the second machining on the workpiece.

Subsequently (FIG. 7, step 4), T1 table, with the new loaded workpiece, is moved to J11 position to perform the first machining on the workpiece in cooperation with H1 head; T2 table is moved to J22 position to perform the second machining on the workpiece in cooperation with H2 head, and T3 table is moved to the loading/unloading position to unload the just finished machining workpiece and reload the new one. This step 4 coincides with the above described step 1, by repeating the machining cycle.

It is clear that the tables moving order in other machining cycles can be different by maintaining the same logic of the invention.

Practically, with the machining center according to the invention, all tables can be neatly machined first by a group and then by the other and it is possible to carry out the loading/unloading steps at a “masked” time during machining

EXAMPLE 2

In some cases, for greater productivity, as shown in FIG. 8, a K machining group can comprise two H and Hbis machining heads to allow parallel machining of two equal or specular P products arranged on the same T table.

For example, by considering the double-headed K2 group and P and P′ double workpiece, an H2 head can be used to perform fast operations, for example milling, while the H2 bis head can perform slower operations, for example smoothing. Thus, the required times for the various steps may result to be particularly balanced.

The machining cycle remains as described above, with the difference that while in the previous example machining K2 group comprised machining by only H2 head, now the same group provides machining consisting of two “parallel” machining operations performed by respective H2 and H2 bis heads.

The operation and machining cycles are substantially the same as that described above, and the diagrams in Figures from 4 to 7 apply also in this case.

EXAMPLE 3

FIGS. 9 and 10 show a further variation of the machining center 10. As in Example 1, there is a bearing structure of the portal type 11 in an intermediate position with respect to the first G guides, and a second bearing structure 111 provided in the second end areas of the first G guides, on the opposite side to the F loading/unloading areas, and facing the ends of said first G guides, without overlapping thereon.

On the portal structure 11, on the front side 12, is provided a said W2 guide, horizontal and orthogonal to the G guides, on which a machining K2 group is arranged, bearing a machining H2 head, such as those described above.

On the end bearing structure 111 is provided a first W1 guide, on which is arranged a machining K1 group, which comprises two machining H1′ and H1′bis heads (the latter is hatched) of a different type with respect to that described so far. In fact each one of these has, in addition to the machining axes provided for the previous heads a further translation axis y1′ parallel to the Y direction, so as to allow machining along this axis when the respective T table with which it interacts has arrived in the end of stroke G guide position, a position wherein the table cannot advance any longer. It is clear that the two H1′ and H1′bis heads can operate also individually on a table and not necessarily in pairs (in any case the K1 group operates on one table at a time, whether it uses one of the two heads, or if it uses them both at the same time).

The operation and the machining cycle is substantially the same as that described above, and the diagrams in Figures from 4 to 7 apply also in this case.

EXAMPLE 4

FIGS. 11 to 17 show a further embodiment of the machining center according to the invention, varying from Example 3, described above.

In this new Example, a new first G4 guide was added for a respective T4 table. Consequently, according to the invention, a third machining K3 group was added (the machining K groups are equal to three in number, that is, one less than the tables).

With respect to the previous Example, portal structure 11 has a second W3 guide on the rear side 13 of the structure, and on that guide there is arranged machining K3 group. In this example there is an H3 head movable along W3 in the x3 direction, similar to the H2 heads of Example 1 or Example 3.

The machining cycle is similar to the previous examples. Reference is made to the new “matrix” diagrams shown in Figures from 13 to 17 (diagrams defined as in the previous Examples). For example, with reference to FIG. 13 (step 1), and referring to a cycle time not corresponding to the machine startup, T1 table is in the machining J11 area, that is, it is interacting with K1 group, or H1′ head and/or H1′bis head, to allow P workpiece, loaded thereon, to undergo a first machining; T2 table is in J22 area where it is interacting with K2 group, that is, H2 head to operate on the respective workpiece a second machining; T3 table is in J33 area where it is interacting with K3 group, that is H3 head to operate on the respective workpiece a third machining; T4 table is in the loading/unloading F40 position to unload a just finished machining workpiece and load a P workpiece to be machined.

Subsequently (FIG. 14, step 2), table 1 is moved to machining J12 position to interact with the machining H2 head (moved to this position from the previous J22 position) and perform the second machining on the workpiece; T2 table is moved to J23 position to interact with H3 head to perform the third machining; T4 table is moved to J41 position to interact with H1′ and/or H1′bis head and perform the first machining of the workpiece, while T3 table instead is moved into the loading/unloading F30 position to unload the workpiece that has undergone machining from H1′ and/or H1′bis, H2 and H3 heads.

Subsequently (FIG. 15, step 3), T2 table, the workpiece thereof having finished machining, is moved to the loading/unloading F20 position to unload the workpiece and load the new workpiece. T3 table is moved from the loading/unloading F30 position to the machining J31 position to interact with H1′ and/or H1′bis head and perform the first machining on the respective workpiece, T1 table is moved to J13 position to interact with H3 head to perform the third machining, while T4 table is moved to machining J42 position to interact with machining H2 head and perform the second machining

Subsequently (FIG. 16, step 4), T1 table, the workpiece thereof having finished machining, is moved to the loading/unloading F10 position, to unload the workpiece and load the new workpiece, T2 table is moved from the loading/unloading F20 position to machining J21 position to interact with H1′ and/or H1′bis head and perform the first machining on the respective workpiece, T3 table is moved to machining J32 position to interact with machining H2 head and perform the second machining, while T4 table is moved to J43 position to interact with H3 head to perform the third machining.

Subsequently (FIG. 17, step 5=step 1), the tables are moved to occupy the positions as at step 1 and restart the cycle.

It is clear that the moving order of the tables in other machining cycles can be different, by maintaining the same logic of the invention.

Practically, with one more table and machining group, the machining steps increase by one step with respect to the previous Examples.

EXAMPLE 5

This Example (FIGS. 18 and 19) is similar to Example 4, that is, it has four first G guides and three machining K groups. In this Example instead of an end bearing structure 111 such as that described in Examples 3 and 4, in the end areas opposite to the loading/unloading F areas there is an end bearing structure of the portal type 11′. T tables can be positioned under this portal structure 11′.

On the rear side 13′ of the portal structure 11′ there is a second W1 guide on which is arranged a machining K1 group having an H1 head similar to the heads described in the first Example.

The machining cycle of the machining center of this Example is similar to that of Example 4, described above.

It is clear that the Examples described up to now can be combined among them. The various machining groups can have one, two or more machining heads.

The number of the first G guides and T tables can be more than four. For example, with five tables it may be possible to use two portal structures that overlap the first G guides, with machining groups arranged on both sides of both portal structures.

In the case of six tables, to such a configuration it can be added an end bearing structure 111 such as that described in Examples 3 or 4.

The type of heads (mono or multi-spindle, tool changing, etc.) for each group, the number of machining axes thereof, type, number and position of tool storages, etc., can be significantly varied, depending on the requirements and the state of the art.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 

What is claimed is:
 1. A machining center, comprising: three workpiece tables; three first guides, which extend parallel to a first direction, each of said three workpiece tables being movable, separately from said other two of said three workpiece tables, along a respective one of said first guides, two second guides, which extend parallel to a second direction orthogonal to said first direction; two machining groups each comprising at least one machining head, each machining group being movable parallel to said second direction along a respective one of said second guides; six machining areas in which said two machining groups can machine said workpieces present on said three workpiece tables, along each first guide there being present two machining areas, one for each machining group, so that each machining group can operate, according to a programmed work cycle, on all of said three workpiece tables; three workpiece loading/unloading areas, one for each workpiece table.
 2. The machining center according to claim 1, further comprising a portal structure comprising a front side and a rear side, said portal structure being arranged orthogonally to said three first guides, one of said two machining groups being provided on said front side or on said rear side of said portal structure and being movable parallel to said second direction, on a respective one of said two second guides.
 3. The machining center according to claim 2, wherein said portal structure is placed in an intermediate position of said three first guides, so that said workpiece tables are movable on said three first guides through said portal structure, passing from said front side of said portal structure to said rear side.
 4. The machining center according to claim 2, wherein on said portal structure there are movable in said second direction: said two machining groups arranged respectively on said front side and on said rear side of said portal structure, on each of said front side and rear side there being arranged a respective one of said second guides, or a single one of said two machining groups arranged on said front or rear side of said portal structure.
 5. The machining center according to claim 1, wherein said at least one machining head of at least one of said two machining groups is of a type: with two machining axes, with a first vertical translation axis and a second horizontal translation axis corresponding to an axis of one of said two second guides on which it is movable, so that, in combination with said two machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with three machining axes; or with four machining axes, with said first vertical translation axis and said second horizontal translation axis corresponding to said axis of one of said two second guides on which it is movable, a third rotation axis and a fourth rotation axis, so that, in combination with said four machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with five machining axes.
 6. The machining center according to claim 1, wherein at least one of said two machining groups comprises a single machining head.
 7. The machining center according to claim 1, wherein at least one of said two machining groups comprises two machining heads, movable independently from one another parallel to said second direction.
 8. The machining center according to claim 1, wherein said three workpiece loading/unloading areas are provided in first end areas of said three first guides.
 9. The machining center according to claim 1, wherein a first one of said two machining groups comprises a single machining head and a second one of said two machining groups comprises two machining heads, movable independently from one another parallel to said second direction, the machining center further comprising: a portal structure comprising a front side and a rear side, said portal structure being arranged orthogonally to said three first guides, said single machining head being provided on said front side of said portal structure, while said other two machining heads, independently movable from one another, being provided on said rear side of said portal structure, each of said three first guides comprising a respective first end area and an opposite second end area, wherein each of said three workpiece loading/unloading areas is provided in a respective one of said first end areas of said three first guides, said rear side of said portal structure facing said workpiece loading/unloading areas, said portal structure being placed in an intermediate position of said three first guides, so that said workpiece tables are movable on said three first guides through said portal structure, passing from said rear side of said portal structure to said front side and vice-versa.
 10. The machining center according to claim 8, further comprising a load-bearing structure provided in second end areas of said first guides, wherein on said opposite side with respect to said first end areas, on said load-bearing structure there being provided at least one of said two second guides for a respective machining group.
 11. The machining center according to claim 10, wherein said load-bearing structure is a portal structure positioned over said second end areas of said first guides, or faces said second ends of said first guides, without being positioned over them.
 12. The machining center according to claim 10, wherein said machining group movable on said load-bearing structure comprises at least one machining head with at least three axes, a first vertical translation axis and a second horizontal translation axis corresponding to said axis of said second guide on which it is movable, and a third translation axis parallel to said first direction.
 13. The machining center according to claim 1, further comprising an electronic control unit on which there is provided a program for managing a cycle of movements of said tables which provides for, for each table: positioning in said corresponding loading/unloading area, to load at least one workpiece onto said table; translation from said corresponding loading/unloading area toward one of said six machining areas along said corresponding first guide and positioning in said one of said six machining areas in which programmed machining operations can be carried out by one of said six machining groups; translation toward another machining area along said corresponding first guide and positioning in said another machining area in which programmed machining operations can be carried out by another of said machining groups; translation toward said corresponding loading/unloading area to unload said workpiece and restart said cycle on a subsequent workpiece from said step corresponding to said positioning in said corresponding loading/unloading area, to load at least one workpiece onto said workpiece table.
 14. A machining center, comprising: three workpiece tables; three first guides, which extend parallel to a first direction, each of said three workpiece tables being movable, separately from said other two of said three workpiece tables, along a respective one of said first guides; two second guides, which extend parallel to a second direction orthogonal to said first direction; two machining groups, one of said two machining groups comprising a single machining head movable parallel to said second direction along a first one of said second guides, and another one of said two machining groups comprising two machining heads movable independently from one another parallel to said second direction along a second one of said second guides; six machining areas in which said two machining groups can machine said workpieces present on said three workpiece tables, along each first guide there being present two machining areas, one for each machining group; three workpiece loading/unloading areas, one for each workpiece table; a portal structure comprising a front side and a rear side, said portal structure being arranged orthogonally to said three first guides, said single machining head being provided on said front side of said portal structure, while said other two machining heads being provided on said rear side of said portal structure, said portal structure being placed in an intermediate position of said three first guides, so that said workpiece tables are movable on said three first guides through said portal structure, moving from said rear side of said portal structure to said front side and vice-versa, said rear side of said portal structure facing said three workpiece loading/unloading areas.
 15. The machining center according to claim 14, wherein said at least one machining head of at least one of said two machining groups is of a type: with two machining axes, with a first vertical translation axis and a second horizontal translation axis corresponding to an axis of one of said two second guides on which it is movable, so that, in combination with said two machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with three machining axes; or with four machining axes, with said first vertical translation axis and said second horizontal translation axis corresponding to said axis of one of said two second guides on which it is movable, a third rotation axis and a fourth rotation axis, so that, in combination with said four machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with five machining axes.
 16. The machining center according to claim 14, wherein said three workpiece loading/unloading areas are provided in first end areas of said three first guides.
 17. A machining center, comprising: a matrix structure comprising matrix columns and matrix rows; three workpiece tables; three first guides representing said matrix columns of said matrix structure, each of said first guides extending parallel to a first direction, each workpiece table being movable along one of said first guides; a portal structure arranged transversely to said first guides and comprising opposite front and rear sides, said portal structure being placed in an intermediate position of said three first guides, so that said three workpiece tables are movable on said first guides through said portal structure, passing from said rear side to said front of said portal structure; two second guides representing said matrix rows of said matrix structure, each second guide being provided on a respective side of said portal structure, each of said second guides extending parallel to a second direction, said second direction being orthogonal to said first direction; two machining groups, each machining group being movable parallel to said second direction along a respective one of said two second guides, wherein a first of said machining groups comprises a single machining head, wherein a second of said machining groups comprises two machining heads, movable independently from one another parallel to said second direction; six machining areas, wherein said two machining groups are configured to machine said workpieces present on said workpieces tables in said machine areas, wherein two machining areas are present along each column of said matrix structure, each machining group can operate on one row of said matrix structure, each machining group can operate on all said three workpiece tables; three workpiece loading/unloading areas, one for each workpiece table, said rear side of said portal structure facing said three workpiece loading/unloading areas.
 18. The machining center according to claim 17, wherein said at least one machining head of at least one of said two machining groups is of a type: with two machining axes, with a first vertical translation axis and a second horizontal translation axis corresponding to an axis of one of said two second guides on which it is movable, so that, in combination with said two machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with three machining axes; or with four machining axes, with said first vertical translation axis and said second horizontal translation axis corresponding to said axis of one of said two second guides on which it is movable, a third rotation axis and a fourth rotation axis, so that, in combination with said four machining axes corresponding to said movement of said three workpiece tables along said respective first guides, said machining center is at least with five machining axes.
 19. The machining center according to claim 17, wherein said three workpiece loading/unloading areas are provided in first end areas of said three first guides. 